Patent GB-498927-A (GB)
Title: Improvements in or relating to tuning control systems for radio receivers and the like
IPC: H03J5/32
Filed: 1937-07-20
Abstract: 498,927. Adjusting wireless apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., RUST, N. M., and HILLS, E. F. July 20, 1937, No. 20087. [Class 37] [Also in Group XL] In a radio receiver of the kind having push button selection of any one of a number of predetermined stations, the total wavelength range covered is divided into sub-ranges each selected by a sub-range selector button while individual wavelengths within the sub-range are each selected by a wavelength selector button, the operation of one sub-range and one wavelength button being required to select any one wavelength. Fig. 1 shows a selector panel for 48 stations in which 12 subranges SR1 .... SR12 are provided, three for the long wave-band (SR1 SR2 SR3) and nine for the medium band (SR4 ... SR12), the subbands being selected by press-buttons SR1 ... SR12. Each sub-band comprises four wavelengths selected by the four buttons WL1 .. WL4, the individual stations being arranged in countries corresponding to each vertical column the choice being such that no country has a selected station in more than one vertical column. Thus depression of one wavelength button (e.g. WL2) prepares a circuit for any station in that column, and depression of a sub-range button (e.g. SR3) prepares a circuit for any of the four stations in that horizontal. column and thus completes the selection of Luxemburg. Fig. 2 shows a practical application to a superheterodyne receiver, the whole unit shown being at a point remote from the receiver proper to which connections are made over concentric cables, one for the aerial AC, one for the radio frequency input SC and one for the local oscillator L.C. The twelve sub-range buttons SR1 ... SR12 operate the signal circuit switches SR1S .... SR12S and the oscillator circuit switches SR1o .... SR12o conjointly, each switch putting a series resonant circuit SL1, SC, .... SL12, SC12, between the aerial and receiver input. Four subsidiary inductances LS1 .... LS4 are associated with each signal switch SR both on the signal and oscillator sides and are so arranged that each combination SL1, SC1 .... SL12 SC12 with LSI .... LS4 gives the four horizontal stations of each of the four vertical columns of Fig. 1. On the three long-wave sub-ranges the oscillator has only condensers OC1 .... OC3 and on the medium band sub-ranges only inductances OL4 ... OL12 are required instead of series tuned circuits. It will be seen that the action of each button SR makes a connection from the aerial through a circuit SL, SC or OC, OL, through the four auxiliary inductances LS or LO to the wavelength switches WL from whence the final selection is made. The control unit may be at the receiver and not remote and may be associated with manual tuning or an A.F.C. system. The sub-range and wavelength buttons are arranged so that depression of one button releases any other button of the same group already depressed ; or a general release button may be provided which also switches off the receiver. The series circuit inductances may be adjustable, and the buttons may also close indicator lamp circuits to illuminate the name of the selected station. One single inductance may be switchably associated with three condensers for the long wave-band and two or three inductances for the nine ranges of the medium band, Fig. 2a (not shown). Constant selectivity may be obtained by the use of a single tapped inductance in the aerial circuit, inductively coupled to a similar inductance constituting the receiver input circuit, Fig. 3 (not shown). Other similar modifications are also described.